Such an engine usually comprises an engine block which delimits combustion chambers connected to an intake circuit comprising a compressor and an exhaust system comprising a turbine for driving the compressor. The engine block is associated with a device for introducing gasoline into the combustion chambers, usually injectors, and with an ignition device in order to initiate, in each combustion chamber, the combustion of the mixture formed by the air from the intake circuit and by the gasoline from the injectors. When the engine is on full load, for example in the acceleration phase, it happens that the combustion of the air-gasoline mixture is not perfect, the compression of the mixture generating, in the combustion chamber, shock waves (explosive combustion or knocking) that could damage the engine.
To solve this problem, it is known practice to enrich the mixture by increasing the quantity of gasoline mixed with the intake air and to retard the ignition. This has the drawbacks of increasing the consumption of gasoline and, departing from the stoichiometric proportions allowing complete combustion of the air-gasoline mixture, of reducing the efficiency of the catalytic converter of the exhaust system which operates optimally when the stoichiometric proportions are maintained. The result of this is increased pollution.